Bug Description

Since the update to version 55, Amazon Prime Video and Magine TV no longer work. I thought the fix solves this problem, apparently I was wrong. It seems also Widevine DRM since version 55 no longer work. This affects Chromium, Opera and Vivaldi because they use all chromium-codecs-ffmpeg-extra.
A downgrade to version 53 restores the function.

Vivaldi via update to version 1.6.689.46-1
Changelog since the second 1.6 release
[Linux] Vivaldi does play proprietary HTML5 video and audio on Ubuntu with chromium-codecs-ffmpeg-extra 55.0.2883.87 (VB-24384)

Debian contains /debian/patches/fixes/widevine-revision.patch, similar patch exists in Arch also, but not in Ubuntu.
Also fix_building_widevinecdm_with_chromium.patch is probably not needed anymore. There isn't similar patch in Arch nor Debian.
Maybe replacing fix_building_widevinecdm_with_chromium.patch with widevine-revision.patch will help